Solar filaments have long been associated with coronal mass ejections and Space Weather phenomena. Filaments are dynamcal, and changes in their overall mass or its distribution could trigger an eruption. However, a comprehensive study of the elemental composition, abundance, and dynamics in a variety of filaments had not yet been conducted. The research work presented here is a detailed study of twenty filaments with various properties, which was conducted by analyzing the absorption due to the filaments in cotemporal He I (10830 A) and Haalpha (6563 A) images. The results show bands of relative helium deficits and surpluses that imply a stratification of filament material, possibly due to neutral atom cross-field diffusion. For more highly-varying material; there is a weak direct relation between a change in absorption and a change in the relative abundance of helium, and erupting filaments exhibit increasing absorption and a spatial homogenization of material in the pre-erupting filament section.